1. Field of the Invention
This invention relates to a proximity detector of the type with two terminals able to be connected to a charging circuit which includes a load put in series with an external, AC or DC, electrical power source in such a way that this source is in a position to supply the load and the detector.
2. Discussion of Background
Such detectors generally include, on the one hand a detector unit that may be inductive, capacitive, photoelectric, etc. to which a processing electronic circuit is connected that is capable of supplying a switch signal in response to the approach or the presence of an object or target and, on the other hand, an electronic power switch connected to the terminals of the detector to determine the opening and the closing of the charging circuit. The switch is commanded by the switch signal in such a way that it is off in the open condition of the detector and on in the closed condition of the detector.
To supply power to the electronic circuits of the detector, a current source is provided that must operate when the detector is open. The current then supplied by the source must be low and stable whatever the conditions of supply voltage and temperature. Furthermore, even when the detector is closed, it must be supplied with a residual voltage which must remain low and well controlled whatever the switched current passing through the power switch and which must vary only slightly with temperature.